Plants are alive and they react to their world! They grow toward light, root down with gravity, grab onto things they touch, and sleep through winter to survive.
🌱Plants React: Stimulus → Response
🤔 Living things sense and react
A stimulus is anything that causes a reaction (light, gravity, touch, water).
A response is how the plant reacts — usually by growing in a certain direction.
🧭Tropisms — Growing in Response
☀️PHOTOTROPISM
StimulusLight
Stems grow toward the light to catch more sunshine.
☀️ houseplant leaning at a window
⬇️GRAVITROPISM
StimulusGravity
Roots grow down, stems grow up — so the plant knows which way is which.
⬇️ a tipped seed still roots downward
🤚THIGMOTROPISM
StimulusTouch
Vines coil around whatever they touch so they can climb.
🤚 pea vine grabbing a fence
🛡️Adaptations That Help Plants Survive
Dry desert 🌵
A waxy skin locks in water and sharp spines guard against thirsty animals.
Shady rainforest 🌴
Big, broad leaves spread wide to soak up the little sunlight under the trees.
Reaching for water 💧
Deep roots dig down for water far below; shallow roots spread wide to grab rain fast.
Defense mechanisms 🛡️
Thorns, prickles, or bad-tasting poison protect a plant from being eaten.
😴Dormancy — Sleeping Through Winter
🔑Key Terms
⚡StimulusSomething that causes a reaction (light, touch, gravity).
↩️ResponseHow a living thing reacts to a stimulus.
🧭TropismPlant growth toward or away from a stimulus.
☀️PhototropismA plant growing TOWARD light.
⬇️GravitropismRoots grow DOWN with gravity; stems grow UP.
😴DormancyA "sleep" state to survive harsh times like winter.
⭐Remember: plants are alive! They sense their environment and respond — growing, climbing, or going dormant — to survive.